Enzymatic glycerolysis production of flaxseed oil-based diacylglycerol in a bubble column reactor and its heat treatment stability

Abstract

Structured lipid diacylglycerol (DAG) synthesis employing bubble column reactor (BCR) is a recent and promising approach used to replace the conventional stirred tank reactor for upscaling purpose. BCR offers great economic benefits in the long run. In the present study, a screened Lecitasse® Ultra (LU) lipase was immobilized (LXTE-LU) and used repetitively in both BCR and stirring system reactor (STR) to catalyze the glycerolysis of flaxseed oil for the preparation of DAG. The BCR system was found to prolong the lipase shelf life, maintaining 69% of catalytic activity after 10 cycles. The reaction products were purified by molecular distillation to obtain DAG-40 and DAG-80. Monitoring of processing contaminants and phytonutrients during the heat treatment of flaxseed oil and flaxseed oil DAG products revealed that prolonged heat treatment significantly increased glycidyl esters levels while short-term stir-frying did not significantly affect the levels of processing contaminants levels. However, prolonged heat treatment destroyed phytonutrients. Meanwhile, the oxidation kinetic study showed that the DAG samples fitted well with the zero-order reaction kinetic model, and the oxidation rate of DAG was lower than that of flaxseed oil. Additionally, the antioxidant effect increased with higher DAG content, indicating that DAG could effectively retard lipid oxidation and improve the stability of the oxidation process. These stabilities suggest the potential application of polyunsaturated DAG in food processing systems.